REGULATION OF BLOOD GLUCOSE

• WHAT HAPPENS WHEN BLOOD GLUCOSE CONCENTRATION IS TOO LOW?

  cells are deprived of energy and die
• WHAT HAPPENS WHEN BLOOD GLUCOSE CONCENTRATION IS TOO HIGH?

  lowers water potential of blood leading to osmotic problems (e.g. dehydration)
• ROLE OF PANCREAS REGULATING BLOOD GLUCOSE?

  produces digestive enzymes and hormones for regulating blood glucose concentration

  -> Islets of Langerhans scattered through (groups of hormone-producing cells - alpha = glucagon, beta = insulin)
• ROLE OF LIVER REGULATING BLOOD GLUCOSE?

  made up of cells called hepatocytes

  1. GLYCOGENESIS: glucose -> glycogen
  2. GLYCOGENOLYSIS: glycogen -> glucose
  3. GLUCONEOGENESIS: glycerol/ AAs -> glucose
• WHERE DOES BLOOD GLUCOSE COME FROM?

  • directly from diet (hydrolysis of carbohydrates = glucose)
  • hydrolysis of glycogen in small intestine stored in liver and muscle cells (glycogenolysis)
  • gluconeogenesis
• ROLE OF INSULIN AND BETA CELLS?

  • receptors detect rise in blood glucose concentration
  • secrete insulin into blood
  • insulin = globular protein
  • all cells except RBCs have glycoprotein receptors (specific to insulin) on CSM
• RESPONSES OF INSULIN?

  • changes tertiary structure of glucose transport carrier proteins (change shape and open) = more glucose into cells by facilitated diffusion
  • increase in number of carrier proteins for glucose transport in cell-surface membrane
  • activation of enzymes converting glycose into glycogen and fat
• HOW DOES INSULIN LOWER BLOOD GLUCOSE?

  • increasing rate of absorption of glucose into cells (especially muscle cells)
  • increasing respiratory rate of cells
  • increasing rate of glycogenesis in liver/ muscle
  • increasing rate of conversion of glucose to fat
• ROLE OF GLUCAGON AND ALPHA CELLS?

  • receptors detect fall in blood glucose concentration
  • secrete glucagon into blood
• RESPONSES OF GLUCAGON?

  • attach to specific protein receptors on cell-surface membrane of liver cells
  • activating enzymes that convert glycogen to glucose
  • activating enzymes involved in conversion of AAs/ glycerol to glucose (gluconeogenesis)
• ROLE OF ADRENALINE?

  raises blood glucose concentration

  • attaching to protein receptors on cell-surface membrane of target cells
  • activate enzymes that cause breakdown of glycogen into glucose in the liver